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Robust Precoding and Postcoding for Multicell Multiuser Transmission using Imperfect CSI
Nguyen-Le, Hung,Nguyen-Duy-Nhat, Vien,Tang-Tan, Chien,Bao, Vo Nguyen Quoc The Korea Institute of Information and Commucation 2016 Journal of communications and networks Vol.18 No.5
This paper studies the problem of precoding and post-coding design for multicell multiuser downlink transmissions in the absence of perfect channel state information (CSI). Using statistical information of imperfect CSI, an iterative multiuser multicell transceiver design is formulated by minimizing the mean squared error (MSE) cost function of signal and leakage interference under per-base station power constraint (PBPC). The convergence of the iterative precoding and postcoding algorithm is verified by analytical and empirical results. The proposed precoding and postcoding algorithm offers a low computational complexity and robustness against CSI imperfection.
Nguyen Phuong Tung,Nguyen Thi Phuong Phong,Nguyen Hoang Duy,Nguyen Quoc Hung 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
This research was conducted to experimentally screen the suitability of acrylamido-2- methylpropane sulfonic acid-acrylamide (AMPS-AM) copolymer-based nanogels for using as sealants to shut-off water channels in the high-temperature and high-salinity reservoir conditions of the White Tiger oil feld. Via in situ intercalative free-radical copolymerization, nanogels have been prepared from montmorillonite-alkyl ammonium clay, AMPS and AM. Two primary compositions of nanogel systems were chosen. A mixture of hexamethylenetetramine (HMTA)/phenyl acetate (PhAc) was used as a crosslinking system. The results obtained from screening the gel properties by using the bottle test method, the test under nitrogen pressure and core ooding under imitated reservoir conditions show that the NANOSEAL-1 and the NANOSEAL-2 nanogels can well satisfy the VietsovPetro (VSP) technical requirements for water isolation materials. This research was conducted to experimentally screen the suitability of acrylamido-2- methylpropane sulfonic acid-acrylamide (AMPS-AM) copolymer-based nanogels for using as sealants to shut-off water channels in the high-temperature and high-salinity reservoir conditions of the White Tiger oil feld. Via in situ intercalative free-radical copolymerization, nanogels have been prepared from montmorillonite-alkyl ammonium clay, AMPS and AM. Two primary compositions of nanogel systems were chosen. A mixture of hexamethylenetetramine (HMTA)/phenyl acetate (PhAc) was used as a crosslinking system. The results obtained from screening the gel properties by using the bottle test method, the test under nitrogen pressure and core ooding under imitated reservoir conditions show that the NANOSEAL-1 and the NANOSEAL-2 nanogels can well satisfy the VietsovPetro (VSP) technical requirements for water isolation materials.
Nguyen Duy-Hung,박선희,김정중 한국방재학회 2018 한국방재학회논문집 Vol.18 No.7
In this article, the effect of latex polymer modification on improving the impact resistance of cement pastes has been investigated. The control cement mixture was proposed with water-cement ratio of 0.5. Based on that, the cement pastes were modified by partially substituting water content with Styrene-Butadiene Rubber (SBR) latex. The mixture ratios were prepared by adjusting the various SBR latex dosages from 5 wt % to 20 wt % of water content. The specimens of modified pastes in the hardened state were tested by Charpy impact experiment and compared to the pure ones after 7, 14, 28, 45, and 60 days of curing. The observation results showed that there is a remarkable improvement in the impact resistance of modified cement pastes. Further, the optimal SBR latex dosage of 10% was proposed.
Safe Reinforcement Learning-based Driving Policy Design for Autonomous Vehicles on Highways
Hung Duy Nguyen,Kyoungseok Han 제어·로봇·시스템학회 2023 International Journal of Control, Automation, and Vol.21 No.12
Safe decision-making strategy of autonomous vehicles (AVs) plays a critical role in avoiding accidents. This study develops a safe reinforcement learning (safe-RL)-based driving policy for AVs on highways. The hierarchical framework is considered for the proposed safe-RL, where an upper layer executes a safe explorationexploitation by modifying the exploring process of the ε-greedy algorithm, and a lower layer utilizes a finite state machine (FSM) approach to establish the safe conditions for state transitions. The proposed safe-RL-based driving policy improves the vehicle’s safe driving ability using a Q-table that stores the values corresponding to each action state. Moreover, owing to the trade-off between the ε-greedy values and safe distance threshold, the simulation results demonstrate the superior performance of the proposed approach compared to other alternative RL approaches, such as the ε-greedy Q-learning (GQL) and decaying ε-greedy Q-learning (DGQL), in an uncertain traffic environment. This study’s contributions are twofold: it improves the autonomous vehicle’s exploration-exploitation and safe driving ability while utilizing the advantages of FSM when surrounding cars are inside safe-driving zones, and it analyzes the impact of safe-RL parameters in exploring the environment safely.
Robust Precoding and Postcoding for Multicell Multiuser Transmission using Imperfect CSI
Hung Nguyen-Le,Vien Nguyen-Duy-Nhat,Chien Tang-Tan,Vo Nguyen Quoc Bao 한국통신학회 2016 Journal of communications and networks Vol.18 No.5
This paper studies the problem of precoding and post-coding design for multicellmultiuser downlink transmissions in theabsence of perfect channel state information (CSI). Using statisti-cal information of imperfect CSI, an iterative multiuser multicelltransceiver design is formulated by minimizing the mean squarederror (MSE) cost function of signal and leakage interference underper-base station power constraint (PBPC). The convergence of theiterative precoding and postcoding algorithm is verified by analyt-ical and empirical results. The proposed precoding and postcodingalgorithm offers a low computational complexity and robustnessagainst CSI imperfection.
긴장 된 강선에서 주변 온도가 전기 임피던스에 미치는 영향
응우옌주이훙 ( Nguyen Duy-hung ),김병화 ( Kim Byeong Hwa ) 한국구조물진단유지관리공학회 2019 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.23 No.2
This paper presents the results of the tests on electrical impedance for the steel wire under the effect of ambient temperature and stress level shift. The experiments are carried out in variable temperature conditions ranging from 30 to 60 ℃ and different stress levels ranging from 10% to 70% of yield strength. The results show the relationship between electrical impedance and temperature is a linear correlation at all stress levels.
Van Hoang, Nguyen,Hung, Chu Manh,Hoa, Nguyen Duc,Van Duy, Nguyen,Park, Inkyu,Van Hieu, Nguyen Elsevier Sequoia 2019 Sensors and actuators. B Chemical Vol.282 No.-
<P><B>Abstract</B></P> <P>Cost-effective fabrication of sensors and detection of ultralow concentrations of toxic gases are important concerns for environmental monitoring. In this study, the reduced graphene oxide (RGO)-loaded ZnFe<SUB>2</SUB>O<SUB>4</SUB> nanofibers (ZFO-NFs) were fabricated by facile on-chip electrospinning method and subsequent heat treatment. The multi-porous NFs with single-phase cubic spinel structure and typical spider-net morphology were directly assembled on Pt-interdigitated electrodes. The diameters of the RGO-loaded ZFO-NFs were approximately 50–100 nm with many nanograins. The responses to H<SUB>2</SUB>S gas showed a bell-shaped behaviour with respect to RGO contents and annealing temperatures. The optimal values of the RGO contents and the annealing temperatures were found to be about 1.0 wt% and 600 °C, respectively. The response of the RGO-loaded ZnFe<SUB>2</SUB>O<SUB>4</SUB> NFs to 1 ppm H<SUB>2</SUB>S gas was as high as 147 at 350°C while their cross-gas responses to SO<SUB>2</SUB> (10 ppm), NH<SUB>3</SUB> (100 ppm), H<SUB>2</SUB> (250 ppm), C<SUB>3</SUB>H<SUB>6</SUB>O (1000 ppm), and C<SUB>2</SUB>H<SUB>5</SUB>OH (1000 ppm) were rather low (1.8−5.6). The high sensor response was attributed to formation of a heterojunction between RGO and ZnFe<SUB>2</SUB>O<SUB>4</SUB> and due to the fact that NFs consisted of many nanograins which resulted in multi-porous structure and formation of potential barriers at grain boundaries.</P> <P><B>Highlights</B></P> <P> <UL> <LI> rGO-loaded ZnFe<SUB>2</SUB>O<SUB>4</SUB> nanofibers have simply prepared by electrospinning. </LI> <LI> rGO-loaded ZnFe<SUB>2</SUB>O<SUB>4</SUB> nanofiber sensors can detect H<SUB>2</SUB>S gas down to ppb level. </LI> <LI> The loading rGO can result in an enhancement of H<SUB>2</SUB>S gas ensing performance. </LI> </UL> </P>